Stereotactic depth electrode placement for chronic subthreshold cortical stimulation: surgical technique video

Neurostimulation is an increasingly common treatment option for medically intractable epilepsy. SANTE (Stimulation of the Anterior Nucleus of the Thalamus for Epilepsy) and Responsive Neurostimulation (RNS) System are landmark neurostimulation trials that utilized either duty cycle or a responsive stimulation paradigm. A seizure-free outcome is rarely observed with responsive and duty cycle neurostimulation devices. Chronic subthreshold cortical stimulation (CSCS) is a promising treatment for adult drug-resistant epilepsy involving eloquent cortex and has demonstrated safety and efficacy. Herein, the authors describe the surgical technique as well as details of stimulation programming involved in CSCS placement to facilitate the adoption of this promising treatment. The video can be found here: https://stream.cadmore.media/r10.3171/2024.4.FOCVID2422

Given colocalization of seizure onset zone and eloquent cortex, a trial of therapeutic stimulation was delivered through stereo-EEG hardware.Here, we show the device used to deliver stimulation through the sEEG contacts.From left to right, we see a clinician programmer, a clinical telemetry module, and the external neurostimulator.The ENS outputs to a custom cable terminating in 16 contacts that are connected to sEEG hardware via stackable touch-proof jumper cables.
During therapeutic stimulation there was a suppression of interictal discharges.Note a reduction in interictal discharges between the 2-Hz stimulation artifact following discontinuation of stimulation on the left side of the EEG tracing.We can see a transient suppression of interictal discharges.
3:06 Rationale for Procedure.So, in this approach, a diffuse seizure onset zone involving multiple eloquent locations and successful prestimulation during sEEG predicted a good outcome with multiple therapies; however, CSCS (chronic or ongoing subthreshold cortical stimulation) was recommended to the patient.We believe this was predicted by the EEG monitoring.The benefits of decreased seizure frequency, preserved neurological function, and generally reversible if unsuccessful were utilized in this particular situation.Although all the listed thera-

Stereotactic depth electrode placement for chronic subthreshold cortical stimulation: surgical technique video
Daniel Jeremiah Harrison, BS, 1,3 Soliman Oushy, MD, 1 Nicholas M. Gregg, MD, 2 Brian N. Lundstrom, MD, PhD, 2 and Jamie J. Van Gompel, MD 1 Departments of 1 Neurological Surgery and 2 Neurology, Mayo Clinic, Rochester; and 3 Mayo Clinic Alix School of Medicine, Mayo Clinic, Rochester, Minnesota Neurostimulation is an increasingly common treatment option for medically intractable epilepsy.SANTE (Stimulation of the Anterior Nucleus of the Thalamus for Epilepsy) and Responsive Neurostimulation (RNS) System are landmark neurostimulation trials that utilized either duty cycle or a responsive stimulation paradigm.A seizure-free outcome is rarely observed with responsive and duty cycle neurostimulation devices.Chronic subthreshold cortical stimulation (CSCS) is a promising treatment for adult drug-resistant epilepsy involving eloquent cortex and has demonstrated safety and efficacy.Herein, the authors describe the surgical technique as well as details of stimulation programming involved in CSCS placement to facilitate the adoption of this promising treatment.
3:48 Cranial Procedure Initiation.Here the patient is placed in a Leksell frame and coregistered with Stealth stereotaxis.We identify our entry points and align these on our subgaleal entry points.We then, in the locations where we're targeting our cortical sites, we affix dog bones to accept our electrodes.We then align the precision aiming device.A cannula is then placed just like we do sEEG.We drill through the skull.And then a customized lead delivery device is screwed into the cannula that allows typical targeting cannula with inner diameters of 1.4 mm to be placed to increase the accuracy of the patient's implant.Once this is done, the inner stylet is removed.We then measure from the back of this cannula.We also measure at the skull to identify the depth of the lead.The lead is then placed into the cortex.We then identify on fluoroscopy the exact location.The lead is then held at the skull, the cannula withdrawn, and it is secured with our dog bone, and then the excess wire is tied down to have galea coverage over our openings.
5:09 Cranial Closure.Once all of our electrodes have been placed, we then tag these with either a series of ties in order to identify our implants when hooking this up to the battery.This is then copiously irrigated and, of course, closed in multiple layers.
5:27 Neurostimulation Placement.We then go to the subclavicular region on that side, make a small incision, plan two fingerbreadths below the clavicle.We then open and make a subfascial battery pocket.
We then tunnel down from the superior cranial incision twice with two separate passers in order to allow electrodes to be passed up from the inferior incision to the superior incision.In this particular circumstance, 4 electrodes are assembled to a singular Intellis battery.The Intellis battery is a pain battery that would allow the stimulation of all 16 electrodes if possible, or multiple, or more complex stimulation parameters.
In this circumstance, the DBS intracranial leads have to be assembled to spine lead extensions, which have very tight occlusions.You have to be very careful when passing these into these areas in order not to break the electrodes.Once this is done, as typical, the booty is passed over and then secured with suture.
We then, of course, check intraoperative impedances in order to determine if the assembly is working correctly.And we again make sure that our electrode assembly is correct.
6:46 Wound Closure.These are then copiously irrigated, and the wounds are closed in multiple layers in order to again prevent infection.
7:02 Disease Background.2][3][4][5] However, a seizure-free outcome is rarely observed with either of those mechanisms or approaches. 4,5Chronic subthreshold cortical stimulation, or what we call CSCS, aims to suppress interictal cortical epileptiform discharges by us-ing continuous electrical stimulation.Unlike RNS, CSCS does not require the use of seizure detection algorithms, which sometimes lacks specificity.Also, CSCS provides continuous stimulation, which is advantageous over the duty cycle simulation paradigms where stimulation is often off for the majority of the time. 6Additionally, CSCS lends the possibility of corticothalamic implants, as demonstrated with this patient, compared to RNS.A trial stimulation is often required before implementation of a CSCS system using temporarily implanted hardware such as depth electrodes.
][8][9] 8:14 Evidence.Although the literature is relatively sparse regarding investigations of CSCS for drug-resistant epilepsy, there are a few studies demonstrating its safety and efficacy.One study is a single-center retrospective review that compared five different neuromodulation strategies for treatment of drug-resistant epilepsy.These neuromodulation strategies included anterior thalamic DBS, centromedian thalamic DBS, RNS, CSCS, and VNS.The study included 159 patients.Overall, there was a 61% seizure reduction and 60% responder rate across all neuromodulation modalities.Notably, in an unadjusted pairwise comparison, the total median seizure reduction was most improved for CSCS when compared to the other neuromodulation modalities.Additionally, cortical stimulation, which includes both RNS and CSCS, was associated with an improved total median seizure reduction when compared to subcortical stimulation, which encompasses anterior thalamic DBS, centromedian thalamic nuclei DBS, and VNS, at 67% vs 52%, respectively. 10nother study investigating the safety and efficacy of CSCS is a case series of 10 adult patients with drug-resistant epilepsy due to various pathologies who underwent CSCS treatment.All patients experienced an uneventful postoperative course and experienced improvement in both seizure severity and frequency. 8n terms of the current state of CSCS availability, there are devices as in this particular paper that can be used to perform CSCS, such as the Medtronic or Boston Scientific devices.9:42 Clinical Outcome.The permanent electrodes are seen in yellow, and they are coregistered to the sEEG implant with seizure onset zone electrodes marked in red.For the permanent implant, 1 lead targeted the anterior nucleus of the thalamus, while 3 leads targeted the cortical seizure onset region.The patient has had 5 clinical seizures over 11 months following device placement, a greater than 90% seizure reduction.